Procedures

EQUILIBRATION

The most fundamental task in dental treatment is functional equilibration; the balanced distribution of occlusal wear over the available dentition. It is here where prophylaxis is achieved or failed. While the causes of dental overgrowths are varied, their continuation may be due to inappropriate equilibration, either by a complete absence of, or due to, poor quality treatment.

Correct equilibration is considerably more than just ‘rasping’; it optimises the available function, reduces opportunity for malocclusion and goes towards ensuring teeth remain as serviceable as possible throughout the animal’s lifetime. Poor quality treatment is not solely aesthetically displeasing, but potentially risks the health of the tissues and structures affected in addition to the health of the patient. Poor quality equilibration is a common cause of failed prophylaxis.

Dental treatment aims to ensure that dentition is free from sharp edges and conformationally balanced to encourage an effective occlusal relationship, by the reduction of the least amount of dental tissues possible. In many instances, over correction of malocclusions may render the animal inappetent, with a risk of hyperlipaemia in donkeys and ponies, or at risk of developing painful dental infections.

Protocols

While it is important to have a routine, professionals need the ability to change routines upon presentation of different disorders, temperaments and even the use of sedation. It may be preferred to initially perform the reduction of sharp enamel points at the lingual and buccal edges of the cheek teeth, but in the case of larger overgrowths, it may make best use of sedation (if used) to perform occlusal reductions first.

A typical routine may lead the professional to commence with the arcades in a sequential order and this has proven effective in terms of efficiency and diligence. Experienced equilibrators typically complete treatment either arcade by arcade, or by procedure i.e. buccal and lingual point reductions in addition to occlusal reductions in the first arcade before moving to the second arcade, or alternatively performing all of the buccal and lingual point reductions in all arcades before then progressing onto the occlusal reductions as required.

It is in the interest of all equids that regular dental assessments take place; commonly this is achieved on a 6-12 monthly schedule.

Juvenile equids and bitted equids under the age of 12yrs, will typically redevelop sharp enamel points within 6 months of previous treatment. In the older population where it is more common that age related pathologies such as periodontal disease exist, 6 monthly treatment to manage these issues may also be warranted.

The floating of routine enamel points must render the animal with an effective, pain free grinding surface. If the sharp edges are reduced inappropriately, the occlusal surface area may be negatively affected. Additionally, there is a risk to the health of the pulp tissue, even at the lateral/medial aspects of the crown.

During neutral incisor contact, the cheek teeth are not in occlusion in normal, routine cases. Occlusion occurs during lateral excursion of the mandible, and so in normal cases, routine transverse ridges should not interfere with jaw movement. It is entirely preferable that individual transverse ridges that are in excess height of those considered normal for that individual animal, be reduced selectively and within normal limits. Indiscriminate treatment (however subtle) applied to the occlusal surfaces of all teeth as routine treatment is rarely justified and should be avoided.

Reduction of multiple transverse ridges rarely improves rostro-caudal movement of the mandible during ridden work and is a misunderstood practice.

Treatment

Take into account three angulations of the instrument head when reducing sharp edges:

1. Approximately parallel to the lateral or medial aspect of the arcade (depending on the arcade being worked on and the location of the enamel points),

2. Roughly 45° to the sharp edge.

3. Horizontal but solely at the peripheral enamel edge.

These instrument strokes when applied accurately and consistently throughout the arcade will serve to reduce only the over erupted portions of enamel, uniformly, leaving the teeth tooth shaped. These principles are the same for manual and electromechanical instruments.

Care must be taken with:

• Maxillary cheek teeth cingula. These are normal anatomical features and should not be reduced in their totality, but rather the floating of the enamel edges is skilfully profiled into the lateral aspect so as not to leave a sharp remainder of areas that have failed to have been floated (lateral rim).

• Mandibular cheek teeth are narrower owing to an absence of infundibulum; reduction of medial/lingual aspects always needs to take dental anatomy into account.

• Displaced/dysplastic/diseased/overgrown teeth may present with pulp material in abnormal locations on the crown.

• Identify anatomical variants such as curve of spee so that pathology may be differentiated; the occlusal aspects of the 3 and 411 in species with acute curve of spee (e.g. donkeys/ponies) may appear higher than the remaining dentition, but would be normal in those cases. Attempts to reduce these teeth would usually cause iatrogenic pulp trauma.

• Staining of the secondary dentine must remain visible during the reduction of dental tissue, even if it has reduced in size and tone. A complete loss of colour is indicative of indirect pulp trauma and irritation of odontoblast processes.

• Occlusal angulation varies within the arcade. It usually starts off at around 9-10° at the rostral cheek teeth, then increases in angle in caudal teeth. While the average angle may be approximately 15°, the range may be 9-20° within the same arcade and is normal.

Rostral profiling

Previously inaccurately termed ‘bit seating’, rostral profiling is the reduction of sharp edges at the rostral aspect of the first cheek teeth. Floating is performed with meticulous care to ensure that the mucosal fold of the buccal commissure does not sustain trauma during mastication and/or bitted work. Normal protocols for tooth reduction should be followed, taking the minimum amount of tissue necessary to achieve a beneficial affect. This should be similar to the treatment of any sharp edge in the cheek teeth arcade. All of the cheek teeth, including those most rostral, play a role in mastication so there is a need for them to be functional in addition to not being a source of discomfort during bitting. The historical trend of excessive reductions, often removing one third to as much as half of the functional occlusal surface are contraindicated and found to be the cause of iatrogenic pulpar insult.

The location of the rostral most pulp horn (as marked by the secondary dentine staining) is of critical importance to profiling in this location. The distance between the rostral edge of the crown and the secondary dentine at pulp horn 6, is roughly the same as the depth of the secondary dentine at that location. If too much tissue is reduced the pulp may be compromised (directly or indirectly). A loss of staining here may give rise to pulpar necrosis.

Post treatment, pulp horn no 6 should still remain visible only on the occlusal surface, and not on the rostral border of the crown.

Equilibration of overgrowths

The amount of dental tissue to reduce must be balanced by the severity of the overgrowth, the indicators of the secondary dentine staining, the need to preserve viable crown and the ability of the crowns to occlude pre and post procedurally in the absence of pain.

It is usually preferable to plan a higher frequency of treatments with the removal of less dental material at each visit.

Suggested protocols for reduction of dental overgrowths:

• Over erupted cheek teeth opposing absent/expired/non-functional counterparts, may be reduced in accordance with the secondary dentine restrictions and following correct procedure (limiting opportunity for thermal damage, pulp trauma, soft tissue injury etc). Further work may be staged at normal or slightly increased intervals.
  Note: with gravity on their side, it is not uncommon for maxillary cheek teeth to erupt faster than expected.

• Overgrowths opposing viable cheek teeth (with sufficient reserve crown) likely to have capacity to regain occlusion may be reduced in line with above, but with the potential for more regular, phased treatments reducing the need to apply treatment in one go. The aim is for viable teeth to remain viable and tooth shaped, with occlusion minimally disrupted and thus reduce the overgrowth within the realms of functionality over time.

In the majority of cases with good conformation, once the mouth is equilibrated for optimal occlusion, there is reduced opportunity for malocclusions to resurface. Should malocclusions fail to respond to treatment, further investigation, especially to the crowns opposing the overgrowths should be sought.

In cases of multiple severe overgrowths, care is required with the reduction of many cheek teeth in one treatment. For every tooth reduced at the occlusal surface, two are potentially taken out of occlusion. From a functional perspective, it is hard not to extrapolate results of cheek tooth loss with life expectancy in older donkeys whereby the loss of 5 cheek teeth (which effectively loses the function of 10 cheek teeth), life expectancy may be around 12 months. Given that dental overgrowths in equids with mandibles fixed at the symphysis frequently occur bilaterally, it is easy to see the capacity for significant reduction in functionality of the beginning of what is essentially the gastric processing plant.

A common presentation in donkeys, would be overgrowths of 1 and 206, 1 and 210, 3 and 408 and 11, known in short as a dental wave formation; this could potentially take 16 teeth out of occlusion if treated without caution in one go. Yet with skilled equilibration, studies show that functional capacity may be increased even where multiple teeth are overgrown.

Complications will be seen if the clinical crown is reduced to the point where a loss of secondary dentine staining has occurred, there is scope for dental pain to result from hydrodynamic movement within the dentinal microtubules. Desiccation in this manner initiates fluid movement and alters the inter-dentinal tubule pressure; these changes are detected by the mechanoreceptors surrounding the odontoblast processes. The stimulation of these nerve fibres is believed to cause pain which may or may not be further confounded by the addition of thermogenesis.

The soft tissue must always be considered during routine floating. It is important to avoid trauma.

The common locations are the:

• tissues caudal and/or lateral to the upper and lower 11

• tissues dorsally or ventrally to the first cheek teeth during rostral profiling

• buccal tissues around the 1/207 and 08

• sublingual tissues when working on the lower arcades.

Contemporary diamond gritted motorised instruments are relatively soft tissue friendly when the instrument and the oral cavity is kept lubricated with water.

Specific considerations

Incisors

Generally, arbitrary reductions to the incisor crowns are discouraged and this is largely due to a lack of supporting data. Malocclusions however, may benefit from clinically reasoned equilibration in the presence of sufficient reserve crown.

The same principles noted for cheek teeth will apply to the reduction of any crown. Subocclusal secondary dentine thickness is between 0.7mm– 6.7mm in the mandibular incisors and 1.5mm–11.7mm in the maxillary; indicating that non-visual reductions including the use of dental cutters/ shears/wires or electromechanical cut off wheels are contraindicated.

UK studies suggest 99% of donkeys with no simultaneous dental disorders and 97% of donkeys with simultaneous dental disorders presented with ventral curvature across all ages. Therefore, it has been suggested that ventral curvature of the incisors is a normal anatomical feature and should not be reduced. However, studies in two endangered species of large donkeys in Portugal, suggest that ventral curvature is pathological and treatment protocols should aim to straighten the bite plane. These conflicting examples advocates that professionals should make clinically reasoned reductions where they are clearly indicated.

It is not uncommon to find pathologies, especially malocclusions, in donkeys where the mandibular and maxillary counterparts are markedly different. For example total wear related loss may be seen in the maxillary incisors, while the height of the mandibular incisors are not excessive to that assumed as normal for the clinical crown. Questions may be asked of how these teeth have worn beyond occlusion?

Studies focussing on the occlusal angulation of incisor teeth in horses suggest that it is a normal feature that differences exist between left and right hand sides, but also in sagittal angulation between maxillary and mandibular arcades, meaning it is thought to be normal that the occlusal surfaces be mismatched between the maxillary and mandibular incisors. These anatomical features are typically lost during reductions, with professionals attempting to duplicate symmetry and identical angulation of the tables in the upper and lower jaw to establish a horizontal bite plane.

There is scientific support for the notion that when the incisors are at neutral during the masticative cycle, the cheek teeth are not in occlusal contact. The contact occurs on lateral excursion of the mandible. The incisors demonstrate separation once the cheek teeth occlusion is extended across the chewing surface. Therefore, there are inherent dangers in performing whole incisor arcade reductions, that incisor occlusion is lost or reduced so much that the cheek teeth are in constant occlusion and this is to be avoided.

Canines

In donkeys, the canine teeth show less sexual dimorphism than horses and ponies, that is to say that they are a relatively common find in females, especially in the mandible. The canine teeth are brachydont and accordingly do not thrive when reduced.

While it is appreciated that canine teeth may be considered long and on occasion sharp, it is ethically questionable to reduce these teeth for the comfort of the professional undertaking the oral examination. Historical trends of reducing the clinical crown to below the height of the incisors, or even to near gum level is contraindicated and professionals should not attempt anything other than a very light profiling of affected area(s).

Wolf teeth

Wolf teeth are a common find in all equids, and may often present in all four triadan locations in donkeys and mules. Reduction of the clinical crowns is contraindicated, if wolf teeth are justifiably found to be the cause of tissue trauma, performance or bitting issues, they should be carefully extracted using sound sedation, in addition to local and regional anaesthesia.

Removal of calculus

Calculus deposition typically occurs local to salivary ducts. Canine teeth, corner incisors and maxillary premolars are commonly affected.

Supragingival

Calculus deposition should be removed routinely as it often contributes to other pathological processes. Supragingival deposits are readily removed by small forceps and/or scalers. Professionals need to take care to avoid soft tissue trauma. It is common for local gingiva to present with gingivitis/ periodontitis and in these cases, handling and treating the area is likely to cause bleeding.

Subgingival

The removal of subgingival calculus deposition in the canines is considered to be an act of veterinary surgery and a painful procedure warranting sedation and analgesia. Subgingival calculus is effectively removed using a selection of scalers.

ODONTOPLASTY

This is the selective modification of the clinical crown, using instruments in order to improve alignment and functional integrity by reducing opportunities for food stasis. Odontoplasty is considered different from the routine reduction of dental overgrowths of hypsodont crowns.

Dental displacements

Early identification of displaced cheek teeth is an important factor in the prognosis for resolution of any suboptimal alignment. If left unidentified and inadequately treated, the displacement will increase in severity, frequently causing diastemata at the mesial and distal interproximal spaces.

In most cases displacements can be easily identified by aligning the arcade with the line of sight.

When examining the mandibular arcades for example, look along the lateral line of the arcade and look for slight deviations. Confirm these by double checking against the medial or lingual aspects and using the secondary dentine staining to check for alignment along the occlusal surfaces.

Protocol

A good knowledge of anatomy is necessary to assess the displacement and to produce a treatment plan. The affected crown will need full examination, knowledge of the degree of abnormality and a decision on the amount of profiling that can be safely achieved.

It is not uncommon for displaced cheek teeth to also be rotated, so care is needed to identify the true orientation of the crown and associated anatomy.

Treatment

In mild displacements, modifications will be required to the affected side of the crown and potentially to adjacent crowns, mesial and distal to the displacement.

In the case of a laterally deviated 409 for example, instruments should be guided parallel to the lateral wall of the tooth, taking care to limit treatment to the peripheral cementum. Similarly, profiling may also take place to the medial wall of the mesial and distal crowns (408 and 410). Pulp exposure and thermal trauma is a concern working in this region of the crown.

In many cases, reduction of any overgrowth and profiling the deviation will help to resolve mild displacements.

The majority of slight to moderately displaced teeth in younger equids, with or without diastemata, may be resolved within a matter of a few weeks to a few months (if not markedly improved) using careful odontoplastic techniques.

In moderate to severe displacements where extraction or alternative approaches have been ruled out, a similar treatment plan may be indicated, but severity and concomitant disease may determine the level of success in terms of restoring alignment.

The instruments of choice for dealing with displacements do not necessarily differ from what would be considered the standard for routine dental treatment. Motorised instruments including a disc and also an applecore shaped lateral burr ensure that clinical crowns may be adequately profiled and the sharp edges reduced even in tight locations.

PERIODONTAL THERAPY

Periodontal disease may exist in the presence or absence of diastemata. Transient gingival inflammation associated with the exchange of deciduous to permanent dentition may not require specific treatment in normal cases.

The primary treatment of periodontal disease should aim at removal of the causative factor to allow for gingival repair. In the case of crowns affected by calculus deposition, removal of the calcified plaque (supra and sub-gingivally if required), curettage of the gingival sulcus, polishing of the crown and if required a topical treatment of saline, chlorhexidine based flush/gel and/or other perioceutics (including antibiotic preparations depending on severity and resources) will help to combat periodontal disease in mild to moderate cases.

Generally, treatments will differ according to cause, severity, location, resources, skill, experience, ability to refer and concomitant disorders.

Treatment of diastemata

A dental chart, or similar record should be completed at each visit to identify the presence of diastema, the stage of periodontal disease, and any treatment carried out. It is important to:

• Carry out examination under sedation to allow improved visualisation and ease of treatment.

• Ensure effective analgesia, which can be systemic (flunixin at 1.1 mg/ kg or phenylbutazone 2.2–4.4 mg/kg), localised (nerve block) or local anaesthetic gels.

• Use periodontal probes as an aid to determine the depth of periodontal pockets.

• All diastema and periodontal disease treatment should commence with thorough and accurate equilibration.

All food material should be removed from diastemata, usually with dental periodontal forceps and flushing with an oral irrigator.

Inclusion of a small dilution of chlorhexidine (0.05% or 1–40 dilution of the 2% concentration) can act as an antiseptic and has excellent residual properties.

The most common treatment options include:

• For mild diastema, treatment may be as simple as correctly floating the mouth to remove causative overgrowths or improving axial alignment of displaced/dysplastic teeth.

• Periodontal dressing material can help to bridge the diastema after all food material has been removed. The application of bridges should follow a similar principal to that for sealing vacated alveolar sockets; space must be left to allow for granulation.
  Packing the diastema via total infill results in interproximal stenting and thus discourages closure of the interproximal space. It is important that bridging is regularly checked and replaced to allow repair of the gingiva underneath and closure of the diastema if normal rostrocaudal angulation of the reserve crown is present. Timescales will vary according to severity of periodontal disease, the age of the patient, the location, number and type of diastemata and the skill of the professional. In juvenile cases, dressing material may become dislodged within a matter of days/weeks. Conversely, in geriatric animals, professionals need to be vigilant in scheduling check-ups as bridges are commonly retained indefinitely.

• Widening and/or parallelising of the interproximal space has been shown to have success in preventing food stasis and even allowing closure of diastemata, especially in cases where the mesial and distal aspects are not parallel. This technique however, demonstrates a high risk of iatrogenic trauma to the pulp tissues, even when performed by trained professionals, owing to anatomical variations in pulp location and limited visualisation even during oroscopically-guided procedures.

• Diastema at displaced cheek teeth may be resolved upon extraction of the affected crowns. The most common displacements in donkeys occur at the mandibular 09s and 10s and can cause significant soft tissue trauma as well as periodontal disease. If extensive periodontal disease is not present, periodontal attachment can be solid and extraction of these displaced teeth should be approached with caution.

EXTRACTIONS

The indications for extraction include:

• Apical infection

• Fracture

• Infundibular caries

• Periodontal disease

• Pulpar exposure

• Anachoretic infection (haematogenous deposition of bacteria into the pulp)

• retained deciduous teeth

• displacement

  • Severe displacements may cause buccal or lingual ulcers
  • Uncontrollable periodontal disease due to food entrapped around the displacement

• supernumerary teeth

• neoplasia

• dysplastic teeth

• equine odontoclastic tooth resorption and hypercementosis (EOTRH).

As with all procedures, the general health status of the donkey must be considered when planning treatment. Quality of life following treatment should be part of the decision process. Consider:

• Young animals have less root definition meaning removal may be more straightforward but more difficult due to length of the reserve crown and density of periodontal ligament attachment.

• Removal of a molar in a young animal will necessitate an increased frequency of routine dental treatment throughout life.

• Geriatric equids may have loose teeth due to decreased reserve crown but root structures can be more fragile meaning increased chance of fracture during extraction.

• Radiography before and after the procedure can aid planning and confirm that no fragments have been left within the socket.

Incisors

For simple extractions, the dental elevators should be advanced between the tooth and the alveolus to cut the periodontal ligament. Slow and steady pressure is applied to further loosen attachments until the tooth can be grasped with forceps and extracted without force.

It is advisable to use several different shapes/lengths of elevator to ensure the entire depth of the periodontal ligament is broken down and the tooth is sufficiently loose before removal is attempted.

Teeth that are difficult to loosen may need to be extracted surgically by incising over the reserve crown and removing the overlying bone using a narrow osteotome or small periodontal elevator. Once the tooth is loose it can then be removed with the extraction forceps and the socket flushed.

Canines

Extraction of canine teeth may be complex and require surgical intervention due to the length of reserve crown and curved root structure.

This often necessitates a lateral alveolar ostectomy via a gingival flap. Care must be taken to remove the entire alveolar bone from the most mesial to distal aspect as this will greatly facilitate the procedure. Once the tooth is exposed a periodontal elevator can be used to break down the remaining periodontal ligament until the tooth is loose enough to be extracted. Once extracted, the bone margins should be smoothed and the alveolus debrided and flushed clean before suturing using a simple interrupted pattern.

Occasionally, canine teeth may present as small subgingival masses, it is often not necessary to incise the gingiva to allow the teeth to erupt. Indeed, female equids may often present with very small and rostrally positioned mandibular canine teeth (which may or may not be subgingival) that cause issues pertaining to evasion during bridling; these teeth may be extracted or more commonly the person responsible for tacking up may be encouraged to administer due care and avoid the bit making contact to the area during bridling.

Wolf teeth

The wolf tooth is a vestigial remnant in equids, and is normally positioned bilaterally, just in front of the 1 and 206. Wolf teeth are a common occurrence in all equids, and may well be present in donkeys in all four cheek teeth rows.

These simple, brachydont crowns typically erupt between 6–18 months of age and may be shed naturally along with the loss of the 06 cap. The topography of wolf teeth varies widely and the clinical crown may hold no indications as to the root structure subgingivally. Indeed, zebra (and consequently their hybrid offspring including Zedonks/Zonkeys and the Zorse) and some appaloosa breed types of horse may present with molarised wolf teeth, which warrant very careful extraction if required and usually require radiography and extraction in a hospital environment.

In horses, the wolf tooth is almost routinely extracted. This is debated with arguments that the wolf tooth (or 05 to attribute its triadan number) serves no useful purpose, cannot be profiled to address soft tissue injury, prevents adequate profiling of the adjacent premolars and may potentially cause bitting issues. Counter arguments state that all extractions and especially those that venture close to a major artery, should be reviewed on a case- by-case basis and have clinical justification.

Subgingival or ‘blind’ wolf teeth are a relatively less common find in donkeys compared to horses, ponies and mules; these teeth are usually identified by visualisation and palpation of a small, hard mass displaced 10–25mm from the rostral border of the first cheek tooth and usually reflects their orientation of laying along the border of the interdental space. Visually, they may even appear similar to the normal palatine rugae, so palpation of the bars of the mouth is indicated during routine examination. Their typical location contributes to increased susceptibility of bit trauma and a higher incidence therefore, of bitted/occupational evasions and demonstrations of pain reactions.

Professionals must be appropriately familiar with equine dental anatomy so that wolf teeth are correctly identified. It is not uncommon for inexperienced professionals to mistake canine teeth for wolf teeth and attempt extractions that are unnecessary.

Indications for extraction of the wolf teeth are that they are:

• loose, fractured and/or infected or otherwise diseased

• previously inappropriately rasped/profiled

• causing trauma to local tissues, or

• causing clear issues with bitting/performance, including (but not limited to):

  • displacements
  • subgingival/blind - unilateral
  • mandibular.

Extraction of the standard maxillary wolf tooth

Patients should have been previously vaccinated against tetanus or tetanus antitoxin administered if necessary at the time of the procedure. Extraction is performed using standing IV sedation, with both local and regional anaesthesia.

A Hausmann's or McPherson style speculum is preferable for wolf tooth extractions.

A long handled elevator/luxator with a very thin, razor sharp and semi- circular head, should be used to advance to the lateral side of the mandibular frame of the speculum, but medial to the maxillary frame, with the preferred index finger along the back of the shaft for maximal control. The instrument should be advanced in line with the crown, starting from the lateral border and proceeding rostrally. This allows the operator to check the nerve blocks are effective and the elevation of the rostral border allows the crown room to move away from the first cheek tooth when elevating the caudal border. Wolf teeth may erupt in very close proximity to the first cheek tooth and it is necessary to elevate rostrally initially to lessen the pressure placed upon the crown and therefore reduce the risk of root fracture.

Elevation should be approached gently, but positively progressive and using the elevator to incise the periodontal ligament as opposed to stabbing type actions. There is a higher risk of fracture of the crown once forceps are applied, so it is preferable to either elevate the crown substantially, or perform the procedure by elevation alone.

Some professionals elect to use dental hammers to tap the elevator apically, this technique demands ultimate confidence in the comprehension of the root direction and structure, sedation and analgesia, prediction of patient reaction and clinician competence to avoid iatrogenic trauma such as nasal fistulation.

The socket should be curetted using a spoon type curette to remove any remaining dental fragments and a visual examination carried out either directly, or using an endoscope/mirror. Following an uncomplicated extraction, patients should not be bitted for up to a week.

It is wholly unacceptable to undertake techniques that aim to ‘flick’ the tooth from the socket. In a ligament with 28,000 fibre bundles per mm2, it is highly likely that most of these procedures result in undesirable crown fracture. It is similarly undesirable to use elevators such as the Burgess style cylindrical ‘apple corer’ instruments, as the nature of such instruments is to elevate at one specific circumference for the entire depth achieved. Wolf teeth are typically not cylindrical and taper towards the root section and therefore such instruments serve to injure healthy supporting soft and hard tissues.

It is detrimental for wolf teeth to be drilled/ground out using conical burrs as this risks iatrogenic damage (including burns) to the alveolar socket bed and surrounding tissues, serving to delay healing.

Wolf teeth should not be removed solely under the use of oral sedation; humane extractions depend upon good IV sedation in conjunction with satisfactory analgesia (IV, local and regional).

Subgingival Wolf Teeth

Wolf teeth may also present subgingivally and often this may relate to them erupting in a horizontial plane. Typically these teeth are also displaced from their normal location and require careful extraction and potentially radiographs to ascertain orientation.

It is advised that patients with subgingival wolf teeth are assessed radiographically to ascertain differential diagnosis and establish the orientation of the crown. Very experienced professionals may however, be confident in estimating crown orientation, and progress to extraction in the absence of radiography.

Following appropriate sedation and analgesia, which should follow guidelines as for the fully erupted wolf teeth, there are typically two approaches to extraction:

• The gingiva overlying the wolf tooth should be incised longitudinally along the length of the tooth. The crown is then either extracted using forceps, or is elevated from the crown end and removed. This technique either requires closure of the extraction site to prevent food/foreign body stasis or opening completely.

• The gingiva and crown should be elevated and incised as one, making a pocket from which to retrieve the tooth. This technique depends on absolute identification of the orientation of the tooth and similarly, closure of the site or complete opening to prevent complications during healing. This technique is used typically where an aesthetically pleasing outcome is desired and aseptic conditions can be met.

Complications associated with this procedure include:

• Fracture of the wolf tooth crown: some professionals advocate leaving the retained fragment in situ, extracting at a future date, or that the fragment often migrates to the gingival surface over time and is easily removed. However, continuation of elevation around the circumference of the retained fragment in the same manner as that used for extraction of the whole crown, will result in a successful procedure. Additionally, in the extraction of mandibular wolf teeth fragments, it is often useful to flush the socket, if the fragment is sufficiently detached, the flush will encourage migration to the top of the socket for extraction. Failure to retrieve fractured apices of wolf teeth may lead to local infection, development of cystic lesions and development/ continuation of bitted signs/poor performance.

• Perforation of the greater palatine artery: this is a risk factor in all maxillary wolf teeth extractions. Professionals should have a robust plan in place with all the required equipment close to hand to enable a swift response in the case of an emergency. Immediate pressure must be applied to the site of the injury. Sedation should be maintained and the equid moved to a quiet stable with their head elevated. Ligation of the vessel is logistically difficult. The use of a rolled up towel or preferably medical gauze for at least 10 minutes (with direct and continuous pressure) to stem the flow of blood from the greater palatine artery should encourage the bleeding to stop.

• Post procedural wolf teeth extraction complications are usually uncommon, but may include minor localised infection, retention of fragments and sequestration which should all resolve following removal of the causative focus.

Deciduous caps

The cap has a function during its attachment to protect the underlying crown and to shield an inter-dental layer of cellular tissue responsible for resorption, bone formation and inflammation. A combination of wear, resorption of the deciduous apex and the eruption of the permanent counterpart all contribute to successful exfoliation of the deciduous cap in most cases. Therefore, removal of deciduous caps should not be undertaken lightly.

It is common for donkeys to fracture cheek tooth caps in a transverse plane and upon first glance this may appear as a singular dominant transverse ridge, professionals need to look for the line of demarcation when examining using a mirror or endoscope. Other common presentations include markedly laterally displaced mandibular caps and those presenting as ‘step’ mouth type crown overgrowths. These presentations are actually fairly normal in donkeys, the deciduous tooth needs to be ‘dominant’ in height for the masticative forces (in conjunction with the aforementioned physiological adaptations) to exfoliate. The laterally displaced mandibular caps may be detached lingually, but firmly attached to the buccal aspects, and may cause significant soft tissue trauma and transient periodontal disease. The height of the deciduous crown should not be reduced and occlusal reductions in normal deciduous teeth may reduce the ability for self-exfoliation.

In juvenile equids where malnutrition is either evident or assumed to have occurred, it would appear that cap retention is more commonplace, but unless there are obvious clinical justifications for removal, then leaving the cap attached with regular monitoring may be a more appropriate plan.

A recent study in deciduous cap identification and removal in racehorses recognised the complexity of the sequential exfoliation and that the age of exfoliation differed markedly from the ages of permanent tooth eruption widely publicised. The study also highlighted some sexual dimorphism with females shedding their caps later than males (Ramzan et al, 2009).

Most standard donkeys exchange their deciduous teeth typically later than horses and ponies, this is usually six months or so but can be as long as 12 months or more in some cases.

Indications for cap removal include:

• a digitally loose cap

• a fractured cap with fragment loss

• a visible and palpable line of demarcation

• malodour/food retention underneath the cap

• significant or obvious retention of the cap.

Permanent Cheek Teeth

Most permanent cheek teeth can be extracted orally, using standing sedation and appropriate analgesia with the donkey restrained in stocks and the head supported by a headstand or hanging head collar.

Occasionally specialist techniques may be necessary, but these will usually be referred to a specialist hospital.

Equipment to be used must be carefully considered, purpose designed pony instruments are available from a few global suppliers, and may be appropriate.

Teeth from older animals with a short reserve crown or teeth that are already substantially loose may often be removed without difficulty (and commonly digitally), but it is often still advisable to follow the steps detailed below to prevent root fracture during extraction. Professionals should also be aware and equipped for instances where teeth are loose owing to a pre- existing fracture. Dysplastic crowns and those with more than superficial infundibular or peripheral caries should be approached with care, due to the risks of further fracture and consequent complications.

The buccal and palatal or lingual aspects of the gingiva should be elevated using a cheek tooth periodontal elevator. Extreme care is required to ensure that the elevator is working to separate the periodontal ligament, and that the mucosa is not being elevated from the underlying bone. Dental spreaders should then be placed into the interproximal space mesial and distal to the affected tooth to loosen the periodontal attachments. The spreaders should be closed slowly and carefully to avoid damage to the teeth and the supporting bone. The spreaders, once closed, may be left in situ to allow stretch and aid breakdown of the periodontal ligament. This important step can significantly reduce the effort required for non-complex extractions; spreaders may be left in situ for as long as they are actively stretching the periodontal ligament. A rubber tourniquet, adhesive bandage or self-locking mechanism can be placed on the end of spreaders or forceps to keep them in place.

Further elevation to the medial and lateral aspects may be attempted depending on personal preference.

Extraction forceps may be used, placing as low as possible on the tooth, with the maximum amount of crown held within the instrument, to minimise the risk of fracture.

The tooth should be checked using a dental endoscope or mirror to ensure the forceps are positioned correctly and are not in contact with the adjacent teeth. Once positioned, the forceps can be fixed using a tourniquet in the same way as the spreaders. The forceps can then be manipulated 5-10 degrees from side to side to facilitate loosening of the tooth. It is advisable to check the tooth during the first few movements to ensure that the forceps are not rotating and grinding away the crown. Movement of the tooth should reflect the breakdown of the periodontal ligament, movements increase in size as the tooth becomes looser. Resist the temptation to apply excessive force or increase the size of movements prematurely as this can result in fracture of the tooth.

As the tooth becomes looser, a ‘squelching’ noise will be heard and foamy blood will appear in the gingival margins around the tooth.

Once the tooth is sufficiently loose within the alveolus, it may be necessary to apply a fulcum, to provide leverage to extricate the tooth.

For long and/or caudal teeth, it may be necessary to direct the tooth medially to give enough room to extract it fully from the alveolus without obstruction from the opposing arcade. There may be instances where the extracted crown requires reduction to facilitate extraction. This is usually attempted using a lateral burr, but may be the only time where dental cutters are of use in contemporary dentistry. Care must be taken in mandibular teeth to ensure the apical part of the tooth is held/supported to ensure it does not fall into the depths of the socket, making retrieval unnecessarily difficult.

The tooth should be inspected to ensure that removal was complete; paying special attention to the apex for fracture identification. The alveolus should be inspected, visually and digitally, for the presence of dental fragments. It is good practice, where resources permit, to use post procedural radiography as a check. Retained fragments may be removed by the use of curettes and /or dental picks to loosen fragments before removing digitally or with long nosed alligator forceps.

Immediately post extraction the alveolar socket should be flushed clean with water, before allowing a clot to form and sealing the socket with dressing material.

It is critical that dressing material should only be placed in the oral 1/2–2/3 of the alveolus, to allow room for granulation tissue to fill from the apical end. Manuka honey may be deposited in the socket prior to sealing with dressing material.

The seal should be removed and replaced every 1-2 weeks, reducing the volume each time, until granulation tissue has filled the socket. The socket must be free of all infected or necrotic material before placing the packing, to avoid subsequent infection.

If the tooth removed was from an elderly animal, the socket may be shallow and so it may not be necessary to place any packing, especially in maxillary teeth as food will be less likely to become trapped. In these cases however, it is often advisable to ask owners to flush the mouth with water (preferably, salt water) daily if the donkey will tolerate it, to remove the accumulation of food and prevent subsequent infection.

One of the most common complications is fracture of the affected tooth with portions of the root remaining in situ within the alveolus.

Removal may be achieved with the use of dental picks intra-orally, however if this is unsuccessful, procedures such as the minimally invasive transbuccal screw extraction (MTE), or intraoral crown segmentation or lastly, minimally invasive trephination with Steinmann pin repulsion may be indicated (although the latter may demonstrate a higher incidence of post procedural complications).

Teeth already compromised by previous fractures or by infundibular caries in the maxillary teeth have an increased risk of fracture during the extraction process. If the tooth fractures at the gingival margin, it can be very hard to extract orally as placement of extraction forceps may not be possible. In these cases MTE techniques are effective and recommended due to the decreased complication rate when compared to repulsion methods.

The MTE procedure is performed by making an incision through the buccinator or masseter muscle into the oral cavity using a specialised trochar. Care must be taken to avoid damage to the facial nerve which due to the thick skin of the donkey is often hard to visualise, even after clipping.

The same steps as for oral extraction are replicated during MTE, initial elevation is essential. Following sufficient elevation, a hole is drilled from the occlusal surface and directed apically. It is essential that the drill is advanced slowly and through healthy dental tissue. Absolute positioning should be confirmed using radiographic guidance.

Once drilled successfully, the cavity is then tapped to the same thread specification as the screw/threaded bar provided in the kit. The threaded bar is advanced through the trochar and screwed into the crown. A sliding hammer is then used externally to withdraw the crown into the oral cavity. Once the tooth is removed, the trochar is extracted and the buccal cavity closed using staples.

Complications

• Incorrect placement of spreaders or forceps can result in damage to adjacent teeth/tissues.

• Excessive force during the extraction process, inexperience and concomitant pathology may result in mandibular fracture.

• Inappropriate use of instrumentation may lead the mucosa being elevated from the supporting bone.

• Extended procedures lead to a higher incidence of sequestration and post procedural complications.

• Premature displacement of the packing material may allow food to impact within the dental alveolus causing discomfort and leading to infection, draining tracts or oronasal fistulae.

• An increased frequency of routine care will be necessary following exodontia of incisors and/or cheek teeth. It is a primary consequence of extraction that the opposing tooth will no longer receive sufficient wear and will therefore be prone to overgrowth. Drift of the remaining teeth into the space left behind is also a common sequalae. While it may appear logical to assume cheek tooth extraction may predispose patients to diastemata formation, studies have shown that there is no significant difference in number of diastema, gingival recession, or periodontal disease between the extraction CT row and the contralateral CT row. Diastema formation during recovery may be transient, or it may be that the remaining adjacent crowns drift in unison. Closure of the interproximal space at the site of extraction typically occurs at a rate of 15% of the original length of extraction space per year. It is recommended that a routine dental check is undertaken every 6 months following exodontia.